1. Field of the Invention
The present invention relates to an irradiation direction control apparatus for a vehicular lamp, which detects the state of a vehicle and compensates the irradiation direction of the lamp to always keep it to a given direction.
2. Description of the Related Art
There is a so-called auto-leveling apparatus which automatically adjusts the irradiation direction of a lamp installed in a vehicle in such a way as to maintain the irradiation direction of the lamp to a predetermined direction even when the inclination of the vehicle changes. This type of apparatus has detection means for detecting the inclination and height of a vehicle which varies depending on the running conditions, the passenger conditions (the number of passengers, the positions of passengers in the vehicle, etc.), and/or the conditions on the carrying capacity. This apparatus computes the amount of a change in the inclination of the vehicle based on information acquired by the detection means, and compensates the initial adjustment values like the irradiation angle of the lamp in such a way that the irradiation of the lamp always becomes a predetermined status, thereby providing predetermined light distribution.
When a load is applied to the rear side of a vehicle due to a change in acceleration while the vehicle is running, for example, the irradiation direction of the lamp, if not adjusted, is shifted upward from the reference direction. In this respect, the inclination angle along the vehicle is obtained and the irradiation axis of the lamp is inclined downward to always keep the irradiation direction of the lamp to the reference direction. That is, so-called leveling adjustment is performed.
Since the conventional auto-leveling apparatus is activated by an automatic switch irrespective of the operational conditions and/or the running conditions of a vehicle, it suffers large power consumption and shorter life.
If the auto-leveling apparatus operates when the engine of the vehicle is running and when an activation switch for the lamp is not set on, the power consumption unnecessarily increases and the life of the apparatus becomes shorter. If the apparatus is fully deactivated in this case, however, it undesirably takes time for the apparatus to be functional immediately after the activation switch of the lamp is later set on.